Vapor-liquid contactor, cryogenic air separation unit and method of gas separation

ABSTRACT

In an vapor-liquid contactor  4   a  for flowing down a liquid along the surface of a packing and contacting said liquid with the vapor while ascending the vapor, the improvement being characterized in that said packing is a non-promoting-fluid-dispersion type structured packing A 1 , A 2  in which various types of thin sheets or tubes for determining the flow direction of the above liquid or vapor is laminated and arranged in the perpendicular direction, and said contactor includes at least one fluid distribution unit E 1 , E 2  formed of a rough distribution part C 1 , C 2  to distribute the liquid roughly and a minute distribution part B 1 , B 2  to distribute the liquid minutely and equally.

TECHNICAL FIELD

The present invention relates to a vapor-liquid contactor adapted toperform a vapor-liquid contact to thereafter separate gas mixture undera cryogenic distillation, and more particularly to a vapor-liquidcontactor for use in the cryogenic air separation unit for carrying outa cryogenic separation of nitrogen, oxygen, argon from air, to acryogenic air separation unit using the vapor-liquid contactor, and to amethod of gas separation using the vapor-liquid contactor.

TECHNICAL BACKGROUND

A distillation column used in a cryogenic air separation unit, etc.includes a packed column, a sieve tray column and the like. Among them,a packed column has an advantage of a low pressure loss (pressure drop)and a low operation cost with comparison to a sieve tray column.Further, the packed column has several advantages in that it canincrease a relative volatility between each components of air by settinga low operation pressure according to its low pressure loss; the lengthof the column can be extended; and thus a high purity of product,especially high purity of argon, can be prepared.

In general, the packed column includes a vapor-liquid contact partformed of a packing, a liquid distributor and the like inside of thecolumn. Such type of structured material is referred to as avapor-liquid contactor in the present specification.

A structured packing of a self-promoting-fluid-dispersion type is widelyused as packing used in the above vapor-liquid contactor.

The self-promoting-fluid-dispersion type structured packing may beprovided by processing a metal sheet made of aluminum and the like to anappropriate flexural finishing, laminating and arranging the sheets in acondition of at least one portion thereof to be inclined from theperpendicular axis to disperse the liquid while flowing in a surface ofthe packing at an angle to the perpendicular axis. Further, it maypromote a dispersion of the liquid by providing corrugations and/orunevennesses and/or holes on the surface of the metal sheet. Structuredpacking is said also regular packing.

Specific examples of the self-promoting-fluid-dispersion type structuredpacking may include self-promoting-fluid-dispersion type structuredpackings 71, 81 as shown in FIGS. 6 and 7. FIG. 6 is what is disclosedin Japanese Patent Publication No. (Sho) 57-36009 and FIG. 7 is what isdisclosed in Japanese Laid-open Patent No. (Sho) 54-16761. In addition,the self-promoting-fluid-dispersion type structured packing is disclosedin Japanese Patent Publication No. (Hei) 7-113514.

The packing disclosed in Japanese Laid-open Patent No. (Sho) 58-11001belongs to a scope of the above-mentionedself-promoting-fluid-dispersion type structured packing. Such packing isshown in FIG. 8 through FIG. 10. The packing is made of a plurality ofthin sheet lattices a, b, c, . . . ; each of the lattices a, b, c, . . .being flexed in a substantially zigzag pattern and formed of thin sheetstrips 13′˜17′ which is inclined to the lattice sections A, B, C, . . .; and these thin sheet strips 13′˜17′ are integrated with a flexuralsection 18′ to which a planner cross section of the lattice is formed.

In order to prepare such a packing, band 28′ made of metal thin-sheet iscut in a parallel strip 30′ connected with a plurality of sections 29′.In this case, the cut-out line portion 31′ connected with an adjacentstrip 30′ has the same length and only half the length is shift withrespect to the adjacent cut line portion 31′. Thereafter, the strip 31′may be possibly separated.

However, there are disadvantages in the above packed column type ofvapor-liquid contactor in that a higher column should be provided andcosts for the production and construction of an apparatus are high, whencompared to the sieve tray column type of vapor-liquid contactor havingthe identical liquid and vapor loads. In this regard, it has beenrequested to develop a vapor-liquid contactor capable to increase aload, without occurring a flooding by increasing the upper limit of theliquid and vapor loads. It has been also requested to develop avapor-liquid contactor enabling to vary the production rate in a broadrange.

SUMMARY OF THE INVENTION

An object of the present invention is to eliminate the above-mentionedproblems of the prior art and to provide a vapor-liquid contactorcapable of increasing the load.

The inventors have conducted extensive experiments using a freon whichis a liquid having a similar viscosity to a cryogenic material of aircomponents such as nitrogen, oxygen and argon. As a result, theinventors have discovered that a low viscosity liquid of theabove-mentioned cryogenic air component is easily dispersed on thesurface of the packing such that a vapor-liquid contact of a highefficiency cab be therefore expected. Also, when a vapor-liquidcontactor having a self-promoting-fluid-dispersion type structuredpacking is used, it is difficult to allow the liquid to flow in thedownward surface (reverse surface) of the inclined part of the packingwhereby a vapor-liquid contact efficiency becomes low. The presentinvention is made on the above discovery.

In the present invention, a vapor-liquid contactor is characterized byusing a non-promoting-fluid-dispersion type structured packing in whichvarious types of thin sheets or tubes for determining a flow directionof the liquid or vapor to the vertical direction are laminated andarranged to conform to the perpendicular direction, and including atleast one fluid dispersion unit which comprises a rough distributionpart to roughly distribute the liquid and a minute distribution part tominutely and equally distribute the liquid.

Further, the present invention is characterized in that the saidnon-promoting-fluid-dispersion type structured packing has a specificsurface area more than 350 m²/m³.

Further, the present invention is characterized in that the minutedistribution part to minutely and equally distribute the liquid isformed with a self-promoting-fluid-dispersion type structured packing.

Further, the present invention is characterized in that the minutedistribution part to minutely and equally distribute said liquid isformed by laminating at least one non-promoting-fluid-dispersion typestructured packing and parallel plane sheet group in the axial directionof the column, where the parallel plane sheet group may be a metal.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type structured packing is formed with athin metal sheet group or a metal tube group. This thin metal sheetincludes aluminum, aluminum alloy, copper, copper alloy, variousstainless steel and the like, where a sheet metal net having more than10 meshes is included.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type structured packing is formed withvarious kinds of plastic based thin sheet group or tube group.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type structured packing has a shapeangled in a flow channel cross-sectional pattern. The angled shapeincludes various shapes of polygons and corrugations of a saw-toothshape and the like.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type structured packing has a triangleshape in a flow channel cross-sectional pattern.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type structured packing has aquadrangular shape such as square, rectangular, trapezoid and rhombus ina flow channel cross-sectional pattern.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type structured packing is hexagonal inthe said flow channel cross sectional pattern.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type packing comprises a wavy thin sheetformed of a curved surface.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type packing has more than two crosssection patterns selected from the group consisting of a triangle, aquadrangle and a hexagon.

Further, the present invention is characterized in that saidnon-promoting-fluid-dispersion type structured packing comprises aplurality of thin sheets arranged by a spacer.

Further, the present invention is characterized in that said thin-sheetor spacer has at least one of corrugations, flutings, grooves,alternating-peaks-and-troughs, and/or holes.

Further, the present invention is characterized in that at least onevapor distributor for distributing the vapor is provided at the bottomof said non-promoting-fluid-dispersion type structured packing.

Further, the present invention is characterized in that said vapordistributor is formed with a self-promoting-fluid-dispersion typestructured packing.

Further, the present invention is characterized in that said cryogenicair separation unit uses the said vapor-liquid contactor.

According to the present invention, there is provided a gas separationmethod, the method comprising the step of separating a vapor mixturecomponent from at least two gas components mixture using a vapor-liquidcontactor, the improvement being characterized in that said vapor-liquidcontactor has a non-promoting-fluid-dispersion type structured packingformed of various types of thin-sheets or tubes to direct the flow ofsaid mixture vertically, arranged in the direction perpendicular to theflow of said mixture; said non-promoting-fluid-dispersion typestructured packing has a specific surface area of greater than 350m²/m³; said vapor mixture and the cryogenic material thereof flow incountercurrent with respect to the surface of the packing under apressure of from 0.08 to 0.4 MPa while performing vapor-liquid contact;and the loads of the vapor and liquid are so determined that superficialF factor is greater than 1.8 m/s(kg/m³)^(½).

Further, according to the present invention, there is provided anothergas separation method, the method comprising the step of separating avapor mixture from at least two gas components mixture usingvapor-liquid contactor, the improvement is characterized in that saidvapor-liquid contactor has a non-promoting-fluid-distribution typestructured packing formed with various types of thin-sheets or tubes todirect the flow of said mixture vertically, arranged in the directionperpendicular to the flow of said mixture; saidnon-promoting-liquid-distribution type packing has a specific surfacearea of greater than 350 m²/m³; said vapor mixture and the cryogenicmaterial thereof flow in countercurrent along the surface of the packingunder a pressure of from 0.4 to 2.0 MPa, while performing vapor-liquidcontact; and the loads of the vapor and liquid is so determined that asuperficial F factor is greater than 1.0 m/s(kg/m³)^(½).

The vapor-liquid contactor according to the present invention uses as apacking a non-promoting-fluid dispersion type structured packing whereinthin sheets or tubes are laminated or arranged along the perpendiculardirection in which various types of shapes for determining a flowdirection of said liquid and vapor streams are formed over theperpendicular direction of thin sheet or tube. The vapor-liquidcontactor includes at least one liquid distributor consisting of a roughdistribution part to distribute the liquid roughly, and a minutedistribution part to distribute the liquid minutely and equally.Accordingly, in the liquid distributor, the descending liquid isuniformly distributed over the whole cross-section of the column.Thereafter, in the non-promoting-fluid-distribution type structuredpacking wherein thin sheets or tubes formed in the perpendiculardirection of flow streams are laminated or arranged in the perpendiculardirection, a sufficient ascending vapor stream channel is assured bycarrying out a vapor-liquid contact, a descending liquid in the surfaceof the packing is smoothly flowed and an uniformity of thin sheet isretained over the whole sections. The whole surfaces of the packing iseffectively used. For this reason, an increase in the pressure loss dueto an increase in a flow resistance of the ascending vapor can bereduced, a occurring of flooding can be prevented, a sufficientvapor-liquid contact area can be assured and an efficient distillationcan be carried out. Accordingly, the load of the liquid and vapor can beestablished highly.

Further, the height of the column can be set lower. The costs requiredfor the preparation and construction of the apparatus can be reduced. Inaddition, the product output can increased and reduced largely.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic view of a cryogenic air separation unit using oneembodiment of the vapor-liquid contactor in accordance with the presentinvention;

FIG. 2 is a schematic view showing one example of the vapor-liquidcontactor used in the cryogenic gas separation unit as shown in FIG. 1;

FIG. 3 is a perspective view showing one example of the roughdistribution part used in the vapor-liquid contactor as shown in FIG. 2;

FIG. 4 is a perspective view showing another example of the roughdistribution part used in the vapor-liquid contactor as shown in FIG. 2;

FIG. 5 is a perspective view showing another example of the roughdistribution part used in the vapor-liquid contactor as shown in FIG. 2;

FIG. 6 is a perspective view showing one example of theself-promoting-fluid-dispersion type structured packing used as theminute distribution part in the vapor-liquid contactor as shown in FIG.2;

FIG. 7 is a perspective view showing another example of theself-promoting-fluid-dispersion type structured packing used as theminute distribution part in the vapor-liquid contactor as shown in FIG.2;

FIG. 8 is a front view showing a further example of theself-promoting-fluid-dispersion type structured packing used as theminute distribution part in the vapor-liquid contactor as shown in FIG.2;

FIG. 9 is a cross-section view of the self-promoting-fluid-dispersiontype structured packing as shown in FIG. 8;

FIG. 10 is a detailed view of the method for preparing theself-promoting-fluid-dispersion type structured packing as shown in FIG.8;

FIG. 11 is a perspective view showing one example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 8;

FIG. 12 is a cross section view showing thenon-promoting-fluid-dispersion type structured packing as shown in FIG.11;

FIG. 13 is a perspective view showing a thin sheet of thenon-promoting-fluid-dispersion type structured packing as shown in FIG.11;

FIG. 14 is a cross-sectional view showing another example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 15 is a cross-sectional view showing a further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 16 is a cross-sectional view showing a further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as-shown in FIG. 2;

FIG. 17 is a cross-sectional view showing a further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 18 is a cross-sectional view showing a further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 19 is a cross-sectional view showing a further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 20 is a cross-sectional view showing a further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 21 is a cross-sectional view showing al further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 22 is a cross-sectional view showing a further example of thenon-promoting-fluid-dispersion type structured packing used in thevapor-liquid contactor as shown in FIG. 2;

FIG. 23 is a perspective view showing a modified example of thenon-promoting-fluid-dispersion type structured packing as shown in FIGS.11 to 13;

FIG. 24 is a perspective view showing a modified example of thenon-promoting-fluid-dispersion type structured packing as shown in FIG.15;

FIG. 25 is a perspective view showing one example of a parallel planesheet group used in the vapor-liquid contactor in accordance with thepresent invention;

FIG. 26 is a perspective view showing another example of a parallelplane sheet group used in the vapor-liquid contactor in accordance withthe present invention;

FIG. 27 shows one example of a vapor-liquid contactor as shown in FIG. 2and the simulation result of distillation operation;

FIG. 28 shows an inner structure of one example of the a vapor-liquidcontactor in accordance with the present invention;

FIG. 29 is a graph showing the experimental result where a horizontalaxis is a superficial F factor and a vertical axis is a pressure lossper unit height;

FIG. 30 is a photograph showing a fluid dropping down from the loweredge of a packing when one example of a vapor-liquid contactor inaccordance with the present invention is used; and

FIG. 31 is a photograph showing a fluid dropping down from the loweredge of a packing when a vapor-liquid contactor in accordance with thecomparative example is used;

In FIGS. 1 to 31, each of the reference numbers is denoted as follows:

2 . . . high pressure column, 2 a, 3 a, 4 a . . . vapor-liquidcontactor,

3 . . . low pressure column, 4 . . . argon column,

41, 51, 61 . . . liquid distributor,

91, 101, 111, 121, 131, 141, 151, 161 . . . non-promoting-fluiddispersion type structured packing,

92, 102, 132, 152 . . . thin sheet,

96, 106, 116, 126, 166 a, 166 b . . . flow channel, 162 . . . tube,

A₁, A₂, A₃ . . . non-promoting-fluid dispersion type structured packing,

B₁, B₂, B₃ . . . minute distribution part,

C₁, C₂, C₃ . . . rough distribution part, E₁, E₂ . . . liquiddistributor, 85, 86 . . . parallel plane sheet group.

EMBODIMENTS OF THE INVENTION

FIGS. 1 and 2 show a cryogenic air separation unit using thevapor-liquid contactor in accordance with the present invention. Thecryogenic air separation unit shown herein comprises a high pressurecolumn 2, a low pressure column 3 and a crude argon column 4. The highpressure column 2 is formed of a vapor-liquid contactor 2 a. The lowpressure column 3 is formed of a vapor-liquid contactor 3 a. Thisvapor-liquid contactor 3 a is divided into each contacting sections 6˜10over the top portion of the column from the bottom portion of the column3. The crude argon column 4 is formed of a vapor-liquid contactor 4 a.Also, a condenser 12 is mounted near the bottom portion in the lowpressure column 3, and a crude argon column condenser is mounted in theupper portion of the crude argon column 4.

Hereinafter, the vapor-liquid contactor 4 a of the embodiment thatconstitutes a crude argon column 4 is explained in detail.

As shown in FIG. 2, the vapor-liquid contactor 4 a is installed in acylindrical container that forms a column, and includes a liquiddistributor E₁ mounted with a minute distributor B₁ downwardly a roughdistribution part C₁; a non-promoting-fluid dispersion type structuredpacking A₁; a liquid collector D; a liquid distributor E₂ mounted with aminute distribution part B₂ downwardly the rough distribution part C₂;and a non-promoting-distribution type structured packing A₂, over thebase portion from the peak portion of the column.

Hereinafter, the liquid distributor E₁ and the non-promoting-fluiddispersion type structured packing A₁ are referred to as a liquiddistribution and vapor-liquid contact portion F₁. The liquid collectorD, liquid distributor E₂ and non-promoting-fluid dispersion typestructured packing A₂ are referred to as a liquid collection,distribution and vapor-liquid contact portion F₂.

The rough distribution part C₁, C₂ is to distribute a descending liquidroughly in order to aim at an uniform over the column cross-section of adescending liquid stream in the column. In the rough distribution partC₁, C₂, a liquid distributor shown in FIGS. 3 to 5 is preferably used.

The liquid distributor 41 shown in FIG. 3 is referred to as a channeltype. Therefore, the distributor 41 comprises a first distribution box42 of rectangular parallelepipeds mounted along a radial direction ofthe column, and a plurality of second distribution boxes 43 ofrectangular in cross-section attached to in intervals along therectangular direction of the distribution box 42 in the downward of thedistribution box 42.

The first distribution box 42 is a box-like material of the upperopening and is provided so that their two ends are formed to reach nearthe inner wall of the column and stored temporally in the inside of adescending liquid. The distribution hole (not shown) which distributesthe liquid in the distribution box 42 to the second dispersion box 43 isprovided near the bottom portion of the distribution box 42.

The second distribution box 43 is a box-like material arranged in theperpendicular direction, and is provided so that their two ends areformed to reach near the inner wall of the column, and the liquidoutflowing through a distribution hole mounted in the bottom portion ofthe column from the distribution box 42 is uniformly dropped over thewhole cross-section.

The liquid distributor 51 shown in FIG. 4 is called as a vapor chimneytype, and includes a liquid receiving tray portion 52 mounted to conformto a horizontal surface, a plurality of cylindrical chimney tubes 53mounted at the upper location of the tray 52, and a plurality of pipebranch part 54 mounted in the downward of the liquid receiving trayportion 52.

The tray portion 52 is formed so that its peripheral part is extended tothe inner wall of the column. The tray portion 52 is provided with aplurality of distribution holes 52 a over the whole section, wherein adescending liquid is temporarily stored in a liquid receiving trayportion 52 and then dropped down in the uniformly dispersed state overthe whole cross-section of the column via a distribution hole 52 a and abranch portion 54 (open pipe in the upper and lower edges). The upperand lower ends of the chimney portion 53 are open, and a vapor ascendingthe inner portion of the column is passed through the upward of a liquiddistributor 51 via the inner part of chimney 53.

The liquid distributor 61 shown in FIG. 5 is referred to as a spraytype, and includes a main tube portion 62 wherein a descending liquid inthe column is in-fluxed, and a plurality of branch pipe portion 63mounted in interval in the longitudinal direction of the main tubeportion 62.

A main tube portion 62 and a branch tube portion 63 are provided so thatthe two ends can reach near the inner wall of the column. The main tubeportion 62 is connected with a liquid receiving portion (not shown)wherein a descending liquid in the column is guided to the main tubeportion 62, and is provided so that a descending liquid can be guided tothe inner of the main tube portion 62.

A branch tube portion 63 is provided so that its inner space iscommunicated in the inner space of the main tube portion 62, and that aliquid in the main tube portion 62 is in-flowed in the branch tubeportion 63. The branch tube portion 63 is mounted with a plurality ofdistribution holes 63 a in interval along the whole longitudinaldirection, and is provided so that a liquid in the branch tube portion63 is dropped down in an uniformly dispersed state along the wholecross-section of the column through a distribution hole.

The minute distribution part B₁, B₂ of the vapor-liquid contactor 4 a isprovided so that a descending liquid roughly distributed by the roughdistribution part C₁, C₂, is further minutely and uniformly distributedalong the whole cross section of the column. The structure of the minutedistribution part B₁, B₂ is explained below.

As the minute distribution part B₁, B₂, a self-promoting-fluiddispersion type structured packing is preferably used. Theself-promoting-fluid dispersion type structured packing is a packinghaving the pattern and structure in which a descending liquid stream andan ascending vapor stream come into a vapor-liquid contact on thesurface of said structured packing, with the liquid stream and the vaporstream being flowed in countercurrent with respect to the main streamalong the axial direction of the column, and the vector of the liquidstream and the vapor stream is produced in the direction perpendicularto the main stream, to thereby promote the mixing of the two and carryout the vapor-liquid contact. The self-promoting-fluid dispersion typestructured packing is also called a packing in which a thin sheet madeof aluminum, copper, alloy of aluminum and copper, stainless steel,various types of plastics and the like is formed in various structuredpatterns to have a block pattern of stacked structure. Further, thepresent invention includes a case when said thin sheet is sheet-likemetal gauge of greater than 10 mesh. Structured packing is also calledregular packing.

The specific examples of the self-promoting-fluid dispersion typestructured packing are shown in FIGS. 6 to 10.

The self-promoting-fluid dispersion type structured packing 71 shown inFIG. 6 is disclosed in Japanese Patent Publication No. (Sho) 57-36009wherein a plurality of thin sheets 72 having a wave pattern formed ofaluminum etc. are arranged in parallel to the axial line of the column,laminated to contact with each other and formed in a block pattern.Therefore, the wavelike groove 73 of each thin sheet 72 is inclined withrespect to an axial line of the column, and an adjacent wave-like thinsheet 72 is arranged so that a direction of forming the wave-like groove73 is intersected. Further, the reference number 72 a denotes a holemounted in a thin sheet 72.

FIG. 7 shows a thin sheet 82 that forms a structural unit of theself-promoting-fluid dispersion type structured packing 81 as disclosedin Japanese Patent Laid-open No. (Sho) 54-16761. This thin sheet 82 ischaracterized in that it forms a wave pattern to make a wave-like groove83 and that the thin sheet 82 is further provided with a fine wave-likegroove 84 formed at a given angle relative to a wave-like groove 83.Further, the reference number 82 a denotes a hole formed by a thin sheet82.

FIGS. 8 and 9 illustrate another example of the self-promoting-fluiddispersion type structured packing which is disclosed in Japanese PatentLaid-open No. (Sho) 58-11001. The self-promoting-fluid dispersion typestructured packing disclosed herein has been developed for the purposeof distributing the liquid so that it may obtain a liquid surface aslargely as possible for the mass and heat exchange. Therefore, thisstructured packing is formed of a plurality of thin sheet lattices a, b,c, . . . ; each lattice a, b, c, . . . is flexed in a zig-zag patternand formed of thin sheet strips 13′˜17′ which are inclined to eachlattice sections A, B, C; these thin sheet strips 13′˜17′ are unitedwith a flexural area 18′ and is a packing forming of a planner crossarea of the lattice; the thin sheet strips 13′˜17′ extended to the flowdirection is an intersecting area 18′; the liquid phase 23′ flowing inthe downward of an intersecting area 18′ through thin sheet strips13′˜17′ is formed so as to convey to thin sheet area of sheet strips13˜17 of adjoining via at least a partial intersecting area 18′.

With respect to the intersecting area 18′, notch 20′, 21′ are formed ofoutside the thin sheet strips 13′˜17′.

The notch 20′, 21′ are disposed in the direction extending thin sheetstrips 13′˜17′ in zigzag pattern, wherein it is formed in a more longthan the width s of the thin sheet strips 13′˜17′ and in a more deeplythan half the width s in the perpendicular direction relative to thethin sheet strips 13′˜17′. Further, the thin sheet strips 13′˜17′ isdirectly laminated and overlapped with each other.

Moreover, the intersecting area 18′ of thin sheet strips 13′˜17′ mayform of a hole and/or a sideward notch. Also, the thin strip of eachthin sheet strips 13′˜17′ which is consecutively connected in zigzagpattern may alternatively form of a hole and/or a sideward notch.

As shown in FIG. 10, the packing is, by introducing a cut net in a thinsheet-like metal band 28′, formed of a plurality of parallel strips 30′connected with a plurality of areas 29′; a twill-like hole 32′ is formedin this cut portion 31′ and then metal band 28′ is extended in thedirection 31′ which is a perpendicular direction relative to strip 30′;a plurality of the resulting thin sheet lattices having a rhombuslattice pattern are laminated and prepared in block pattern.

This packing has advantages in that despite a low material cost, a largepacking surface may be obtained. Such advantages is apparent that inview of the structure of thin strips, the thin strips have a largesurface in comparison to a material cost.

Next, the structure of the non-promoting-fluid dispersion typestructured packing A₁, A₂ is explained in detail.

The non-promoting-fluid dispersion type structured packing is a packingin which a liquid stream descending in the column and a vapor streamascending in the column are flowed in countercurrent with respect totheir surfaces, and it has a pattern and structure for carrying out avapor-liquid contact, without promoting mixing of the liquid stream andvapor stream in the direction of the cross-section vertical to the axisof the column. A plurality of thin sheets, tubes and the likedetermining the flow direction of said liquid and vapor is arranged inparallel to the main flow direction (column axial direction).

The materials of said thin sheets and tubes may include aluminum,copper, alloy of aluminum and copper, stainless steel, various kinds ofplastics and the like. Among them, a easily moldable metal is preferablyemployed.

Moreover, the main streams denote a liquid stream descending along theaxial direction of the column and vapor stream ascending along the axialdirection of the column. The main streams also denotes a flow in theaxial direction relative to the flow of material transfer which isproduced on the surface (i.e., surface layer) of the liquid stream andthe vapor stream in the packing surface.

Specific examples of the non-promoting-fluid dispersion type structuredpacking A₁, A₂ are shown in FIGS. 11 to 24.

In the non-promoting-fluid dispersion type structured packing 91 shownin FIGS. 11 to 13, the thin sheet 92 is laminated as a plurality oflayers and the laminated layers are fixed each other by a wiper-band 95.

The thin sheet 92 is subjected to a flexural finishing of the thin sheetformed of said metal, plastics and the like and is formed of a pluralityof parallel grooves 93 in interval.

The groove 93 is formed so that the width is slowly narrowed in thedepth direction. The groove 93 comprises a inclined portion 93 arelative to the bottom 94 and a parallel bottom portion 93 b relative tothe bottom portion 94.

In the thin sheet 92, the bottom portion 94 and groove 93 are laminatedin opposite direction. In the non-promoting-fluid dispersion typestructured packing 91, a space of thin sheet 92, i.e., a space ofcompartment by opposite two groove 93 or by opposite two bottom portion94 has a hexagonal pattern in the cross section. This space becomes aflow channel 96 of an ascending vapor and a descending liquid at thetime of distillation operation.

The non-promoting-fluid dispersion type structured packing 91 isprovided in the inner of the column so that a thin plate 92 is disposedin parallel to the column axial (perpendicular) direction which is amain flow direction.

In the non-promoting-fluid dispersion type structured packing 101 shownin FIG. 14, a plurality of triangle flexural sheets 102 made bysubjecting a thin sheet formed of said metal, plastics and the like to aflexural finishing and then molding them in a triangle wave-pattern, arelaminated through a plate-like spacer 103 formed of metal, plastics andthe like, and these are fixed each other via a wiper-band 95.

In the non-promoting-fluid dispersion type structured packing 101 shownherein, the position of a triangle flexural sheet 102 is determined sothat the top 102 a of triangle flexural sheet 102 is positioned near thebottom portion 102 b of the adjacent triangle flexural sheet 102. Inthis non-promoting-fluid dispersion type structured packing 101, atriangle flexural sheet 102 having a triangle wave pattern is laminatedthrough a sheet-like spacer 103. Therefore, the space between a triangleflexural sheet 102 and spacer 103 forms a plurality of flow channels 106having triangle cross-section which forms a compartment by the triangleflexural sheet 102 and spacer 103.

The triangle flexural sheet 102 may form so that a cross-section shapeof flow channel 106 is in a regular triangle. For example, this may beformed in an equilateral triangle and in an inequilateral triangle.

In the non-promoting-fluid dispersion type structured packing 111 shownin FIG. 15, the position of the triangle flexural sheet 102 isdetermined so that the top portion 102 a of the triangle flexural sheet102 and the top portion 102 b of the adjacent triangle flexural sheet102 are separated each other. In this respect, the non-promoting-fluiddispersion type structured packing 111 is different from saidnon-promoting-fluid distribution type structured packing 101.

In this non-promoting-fluid dispersion type structured packing 111, aspace between a triangle flexural sheet 102 and a spacer 103 forms aplurality of cross-section triangle flow channels 116 which form acompartment by the triangle flexural sheet 102 and spacer 103.

In the non-promoting-fluid dispersion type structured packing 121 shownin FIG. 16, a triangle flexural sheet 102 is stacked, not interposing aspacer 103, in the non-promoting-fluid dispersion type structuredpacking 101 shown in FIG. 14.

In this non-promoting-fluid dispersion type structured packing 121, theposition of a triangle flexural sheet 102 is determined so that the topportion 102 a of the triangle flexural sheet 102 is arranged, in thesame manner as packing 101, near the bottom portion 102 b of theadjacent triangle flexural sheet 102. Therefore, a space between thetriangle flexural plate 102 forms a cross square flow channel 126 whichhas a shape combined with a cross-section triangle flow channel 106.

In that case, the triangle flexural sheet 102 may form so that thecross-section of the flow channel 126 forms various types of shapes suchas a square, a rectangle, a trapezoid, a rhombus, etc.

In the non-promoting-fluid dispersion type structured packing 121′ shownin FIG. 17, the position of a triangle flexural sheet 102 is determinedso that the top portion 102 a of the triangle flexural sheet 102 and thebottom portion 102 b of the adjacent triangle flexural sheet 102 areseparated each other. A plurality of spacers (not shown) may beinterposed in interval in the column axial direction between thesetriangle flexural sheets 102.

In the non-promoting-fluid dispersion type structured packing 131 shownin FIG. 18, the thin sheet formed with said metal, plastics, etc. issubjected to a flexural finishing, a plurality of wave sheets 132 formedin a wavy pattern having curved surface are stacked, and these are fixedeach other via wiper-band 95. The wave sheets 132 formed thatalternating-peaks-and-troughs, are provided of curved pattern in crosssection.

In the non-promoting-fluid dispersion type structured packing 131 shownin FIG. 18, a peak and bottom in the wavy pattern is rounded at the eachcorner thereof. The position of a wave sheet 132 is determined so thatthe top portion 132 a of wave sheet 132 is arranged near the bottomportion 132 b of the adjacent wave sheet 132.

The non-promoting-fluid dispersion type structured packing 141 shown inFIG. 19 is to arrange a spacer 103 between wave sheet 132 in saidnon-promoting-fluid dispersion type structured packing 131.

In the non-promoting-fluid dispersion type structured packing 151 shownin FIG. 20, the wave sheet 152 is formed in a wave pattern having aplane sheet portion 152 a and a flexural curved portion 152 b in asubstantially vertical direction relative to spacer 10. In this respect,the non-promoting-fluid dispersion type structured packing 151 isdifferent from said non-promoting-fluid dispersion type structuredpacking 141.

In the non-promoting-fluid dispersion type structured packing 161 shownin FIG. 21, a cylindrical tube 162 formed of said metal, plastics andthe like is collected, and they are fixed each other via a wiper-band95.

In this non-promoting-fluid dispersion type structured packing 161, theinner portion of the tube 162 forms a cross-sectional cylindrical flowchannel 166 a. Also, the portion of compartment by a peripheral sectionof the tube 162 forms a flow channel 166 b.

Further, the shape of the tube 162 may include polygon such as an oval,a triangle, a square and the like, but these are not particularlylimited to aforesaid shapes. The non-promoting-fluid dispersion typestructured packing 171 shown in FIG. 22 is to combine thenon-promoting-fluid dispersion type structured packing 91 shown in FIGS.11-13 with the non-promoting-fluid dispersion type structured packing111 shown in FIG. 15. The packing 171 includes a flow channel 96 ofcross section hexagon and a flow channel 116 of cross-section triangle.

Where these non-promoting-fluid dispersion type structured packings 91,101, 121, 121′, 131, 141, 151, 161, 171 are provided in the innerportion of the column, all the flexural shapes of sheets 92, 102, 132,152 forming these packing are in the perpendicular direction, and spacer103 and tube 162 are arranged in parallel in the column axial(perpendicular) direction which is a main flow direction.

In the packing shown in FIGS. 14, 15, 19, 20 and 22, if spacer 103 canbe determined by a relative position of thin sheet, not conforming fromthe top edge to the bottom edge of the longitudinal cross-section of onepacking block is acceptable and it may serve as a spacer partiallyinterposed between thin sheets. The thickness of spacer 103 may rangefrom 0.2 to 0.5 mm.

The thin sheet and spacer that constitute the non-promoting-fluiddispersion type structured packing may include at least one ofcorrugations, grooves and/or holes in order to increase a vapor-liquidcontact efficiency. Specific examples are shown in FIGS. 23 and 24.

FIG. 23(a) shows a structure mounted with a hole 92 a in the thin sheet92 in the same manner as that employed in the non-promoting-fluiddispersion type structured packing 91.

FIG. 23(b) shows a structure provided with corrugations of a sawtoothshape 92 b in the thin sheet 92.

FIG. 23(c) shows a structure provided with corrugations of a grooveshape 92 c in the thin sheet 92.

FIG. 24(a) shows a structure mounted with a hole 103 a in the spacer 103in the same manner as that employed in the non-promoting-fluiddispersion type structured packing 111.

FIG. 24(b) shows a structure provided with saw-toothed corrugations 103b in the spacer 103.

FIG. 24(c) shows a structure provided with grooveshape corrugations 103c in the spacer 103.

Further, the thin sheet and the space may have all of or anycombinations of saw-tooth, and groove-shaped corrugations, and holes.

The specific surface area of the non-promoting-fluid dispersion typestructured packing is more than 350 m²/m³ and preferably more than 500m²/m³. When the specific surface area is less than 350 m²/m³, avapor-liquid contact efficiency, the distillation efficiency and theproduct purity will be lowered. Further, the thickness of said thinsheet and tube ranges preferably from 0.1 to 2.0 mm, considering astructural strength.

Turning to FIG. 2, since the liquid collector D of the vapor-liquidcontactor 4 a collects a descending liquid in the column, it includes aplurality of inclined sheet 181 for collecting a descending liquid.

A vapor-liquid contactor 2 a that constitutes a high pressure column 2,and a vapor-liquid contactor 3 a that constitutes a low pressure columnmay be formed in the same structure as said vapor-liquid contactor 4 a.

Further, the vapor-liquid contactor 2 a, 3 a, 4 a is not particularlylimited to the above constitutions and they may include a liquiddistribution and vapor-liquid contact portion F₁ formed of a liquiddistributor E₁ and a structured packing A₁.

In addition, the vapor-liquid contactor 2 a, 3 a, 4 a may be providedwith a plurality of liquid collection and distribution-vapor-liquidcontact part F₁ formed of a liquid collector D, a liquid distributor E₂and a structured packing A in the downward of a liquiddistribution-vapor-liquid contact portion F₁.

Further, each section 6˜9 of the vapor-liquid contactor 3 a may includeone or a plurality of said liquid-collection distribution-vapor-liquidcontact part F₂. A section 10 which is a section adjacent to the top ofthe column is not required to provide with said liquid collector D. Thatis, a section 10 which is most adjacent to the top of the column mayinclude a liquid distribution-vapor-liquid contact portion F formed of aliquid distributor E₁ and a structured packing A₁. Further, in additionto said structure, the bottom of each column may be provided with theminute distribution part B₁, considering a distribution of ascendingvapor. A minute distribution part B₁, B₂ may include aself-promoting-fluid dispersion type structured packing as mentionedabove. For example, a minute liquid distribution may be carried out byproviding a packing of a pattern shown in FIGS. 8˜10 with a layer or aplurality of layers. The detailed structure, characteristic and effectsof such packing are disclosed in Japanese Patent Laid-open No. (Sho)58-11001. Such packing may suitably be used in a liquid distributor anda minute distribution part, but it may also be used in a conventionalvapor-liquid contactor.

Next, one embodiment of the method of gas separation in accordance withthe present invention is described. This embodiment includes a method bywhich each component present in the raw air which is a vapor mixtureincluding nitrogen, oxygen and argon is separated from other componentby a cryogenic air separation by using a cryogenic air separation unitshown in FIGS. 1 and 2. In the embodiment shown herein, a vapor-liquidcontactor 2 a, 3 a may include a liquid distribution-vapor-liquidcontact part F₁ and a liquid collection distribution vapor-liquidcontact part F₂, in the same manner as a vapor-liquid contactor 4 a.

Further, a non-promoting-fluid distribution type structured packing A₁,A₂ may include a non-promoting-fluid dispersion type structured packing91. A minute distributor B₁, B₂ may include a self-promoting-fluiddispersion type structured packing 71. A rough distributor C₁, C₂ mayinclude a liquid distributor 41.

First, a raw air {circle around (1)} is fed into the lower part of ahigh pressure column 2 through a tube channel 1. The raw air symbol{circle around (1)} is usually pressurized at about 0.6 MPa in whichimpurities such as water and carbon dioxide is removed through apretreatment device using an adsorbent such as silica, alumina gel,molecular sieve, etc., cooled to a given temperature via a main heatexchanger and then fed in a high pressure column 2.

The raw air fed in a high pressure column 2 is ascended as an ascendingvapor to the inner portion of the high pressure column 2. Thevapor-liquid contactor 2 a is contacted with a descending liquiddescribed below to conduct a distillation. By doing so, the raw air isseparated into a nitrogen gas (low boiling point component) at the peakof the column and an oxygen-enriched liquid air (high boiling pointcomponent) at the base of the column. The inner pressure of a highpressure column 2 may range from 0.4 to 2.0 MPa, for example, when saidnon-promoting-fluid dispersion type structured packing A₁, A₂ has aspecific surface area of 500 m²/m³. In that case, a superficial F factormay be determined to be more than 1.0 m/s (kg/m³) and preferably1.01˜1.6 m/s (kg/m³)^(2/1).

The nitrogen gas separated in the top portion of a high pressure column2 is discharged from a high pressure column 2 through a tube channel 12a, introduced into a main condenser 12 and then subjected to a coolingand liquefied. Thereafter, a part thereof is returned to a high pressurecolumn 2 through a tube channel 12 b, 12 c to form a descending liquid(reflux liquid) flowing down in the inner portion of a high pressurecolumn 2, and the remaining other part is discharged outside the columnthrough a tube channel 23.

Hereinafter, the process by which a distillation is conducted by acontact of a descending liquid and a ascending vapor in the innerportion of a high pressure column 2 is described.

First, the descending liquid is stored in a firstdispersion/distribution box 42 of a rough distribution part C₁,transferred to a second dispersion box 43 through a distribution hole,stored in said dispersion box 43, and then dropped in the downward of arough distribution part C₁ in the uniformly dispersed state (roughlydispersed state) over the whole cross-section of the column through thedistribution hole provided in the bottom portion.

Then, the descending liquid is transferred to a minute distribution partB₁, spread on the surface of a thin sheets 72 of theself-promoting-fluid distribution type structured packing, and thendropped in the downward of the self-promoting-fluid distribution typestructured packing in the more minutely and uniformly distributed state.In that case, the descending liquid and ascending vapor in the columnare contacted to make a mass transfer between vapor and liquid and carryout a distillation.

Next, the descending liquid is transferred to the non-promoting-fluiddispersion type structured packing A₁ (packing 91) and then flowed downon the surface of a thin sheet 92. In that case, the descending liquidis flowed down on the surface of the thin sheet 92 along the thin sheet92. In that process, the descending liquid is contacted with anascending vapor in the column.

In a vapor-liquid contactor 2 a shown herein, a thin sheet 92 of thepacking 91 is disposed to conform to the main flow upward (perpendiculardirection) as described above; therefore, all the descending liquid inthe packing A₁ follow to conform to this direction. For this reason, theflow of the descending liquid is not in disorder and the liquid streambecomes uniform and smooth over the whole section of a spacer and thinsheet 92.

Accordingly, it is possible to prevent from narrowing the flow channelof the ascending vapor due to the disorder of the descending liquid,that enables to assure a sufficient flow area of the ascending vapor, torestrain an increase in pressure loss with an increase in flowresistance of the ascending vapor, and to carry out a distillation, notoccurring a flooding. Further, the descending liquid that flows thesurface of the thin sheet is easily broaden on the whole thin sheet; abroad contact area of the vapor-liquid is performed; and an efficientdistillation is carried out.

In contrast, in the vapor-liquid contactor using only aself-promoting-fluid dispersion type structured packing, at least a partof the thin sheet is inclined relative to the main flow direction(perpendicular direction); therefore, it is easy to occur a floodingunder a high load, the descending liquid is difficult to flow in thebackside (reverse side) of the inclined part, vapor-liquid contact areais not sufficient, and the distillation efficiency is lowered.

The descending liquid via the non-promoting-fluid dispersion typestructured packing A₁ is collected in a liquid collector D, introducedinto a rough distribution part C₂, in which an uniform flow is made,then flowed in the downward via the self-promoting-fluid dispersion typestructured packing B₂ and the non-promoting-fluid dispersion typestructured packing A₂ to reach the bottom portion of the column.

In the non-promoting-fluid dispersion type structured packing A₂, thedescending liquid is smoothly and uniformly flowed on the surface of thethin sheet 92; therefore, a distillation is carried out in the highpressure column 2, not occurring a flooding. Further, a highdistillation efficiency is maintained.

A part of the liquid nitrogen discharged outside a high pressure column2 through a tube channel 23 is introduced into a low pressure column 3as a reflux liquid nitrogen{circle around (2)} via a valve 24 and a tubechannel 25 to form a descending liquid descending in the low pressurecolumn 3. The other part is discharged outside the system as a productliquid nitrogen (LN₂{circle around (3)}) via a tube channel 22.

The oxygen-enriched liquid-vapor separated in the bottom portion of ahigh pressure column 2 is discharged from a high pressure column 2 via atube channel 15, a part of which is introduced into a crude argon columncondenser 13 via a tube channel 16, wherein a vapor or liquid in thecondenser 13 is subjected to a heat exchange and a heated part isvaporized and then introduced into the middle portion of a low pressurecolumn 3 (a middle portion between the top and bottom of the column) viaa tube channel 31 to make a descending liquid or an ascending vapor in alow pressure column 3.

The other portion of oxygen-enriched liquid air discharged from a highpressure column 2 is introduced into the middle portion of a lowpressure column 3 through a tube channel 17, a valve 18 and a tubechannel 19 to form a descending liquid or an ascending vapor in a lowpressure column 3.

The descending liquid and the ascending vapor introduced into a lowpressure column 3 are contacted each other in each section 6˜10 of thevapor-liquid contactor 3 a, and oxygen gas and liquid oxygen areseparated near the bottom portion of the column and separated into anitrogen gas in the top portion of the column.

Where a non-promoting-fluid dispersion type structured packing A₁, A₂ inthe low pressure column 3 has, for example, a specific surface area of500 m²/m³, the inner pressure of a low pressure column 3 can range from0.08 to 2.0 MPa and preferably from 0.08 to 0.4 MPa. In that case, asuperficial F factor can be more than 1.8 m/s (kg/m³)^(½) and preferablyfrom 1.8 to 2.5 m/s(kg/m³)^(½).

In each section 6˜10 of the vapor-liquid contactor 3 a in the lowpressure column 3, a descending liquid is smoothly and uniformly flowedon the thin sheet surface of packing A₁, A₂; therefore, in the lowpressure column 3 a distillation is carried out without occurring aflooding. Further, a high distillation efficiency is maintained.

The nitrogen gas separated in the peak portion of a low pressure column3 is discharged outside the system as a product nitrogen gas (GN₂{circlearound (4)}) through a tube channel 21. Further, the oxygen gasseparated in the bottom portion of a low pressure column 3 is dischargedoutside the system as a product oxygen gas (GO₂{circle around (5)})through a tube channel 32. In addition, the gas separated in the upperportion of a low pressure column 3 is discharged outside the system as awaste nitrogen gas (WG{circle around (6)}) through a tube channel 20.

A vapor in a low pressure column 3 wherein a some lower position than aposition which said tube channel 31 is connected with a low pressurecolumn 3, is fed in the lower portion of crude argon column 4 through atube channel 26. The gas fed in a crude argon column 4 is distilled inthe vapor-liquid contactor 4 a that constitutes a crude argon column 4,and the crude argon gas is separated in the top portion of the column.Such crude argon gas is discharged from the top portion of the crudeargon column 4 through a tube channel 33, introduced into a condenser13, subjected to a heat exchange with an oxygen-enriched cryogenic airintroduced in the condenser 13 through said tube channel 16, subjectedto a cooling and liquefied, and then returned to the upper portion ofcrude argon column 4 as a reflux through a tube channel 34, 35.

A part of the cryogenic crude argon discharged from a condenser 13through a tube channel 34 is discharged outside the system as a liquidcrude argon (LAr{circle around (7)}) through a tube channel 29. Theliquid separated in the bottom of crude argon column 5 is returned to alow pressure column 3 through a tube channel 27, 28. Moreover, when acorresponding theoretical plate is established largely, a pump 14 can beprovided in the tube channel 27, 28 such that the bottom liquid of thecolumn is returned to a low pressure column 3.

In the vapor-liquid contactor 4 a in the crude argon column 4, adescending liquid is flowed smoothly and uniformly on the thin sheetsurface of the packing A₁, A₂; therefore, a distillation is carried,without occurring a flooding in the crude argon column 4. Further, ahigh distillation efficiency is maintained. Moreover, a crude argoncolumn 4 is set to the substantially same number of theoretical platesas in the prior art reference. Hence, it has recently been adopted thatan oxygen in the rough argon is eliminated by providing a deoxidizingcolumn. In this case, the de-oxidizing column is disposed in a structureas shown in FIG. 2 and the above mentioned effects can be achieved.

In said vapor-liquid contactor 2 a, 3 a, 4 a, various types of thinsheets that constitute a non-promoting-fluid dispersion type structuredpacking A₁, A₂ is disposed such that its pattern is along a main flowdirection (perpendicular direction), So, a sufficient ascending vaporflow channel is assured, and a descending liquid in the surface of athin sheet (or tube) plate 92 is smoothly and uniformly flowed along thewhole section of the thin sheet.

For this reason, it can be prevented from occurring a flooding whichresists an increase in the pressure loss due to an increase in a flowresistance of the ascending vapor. A sufficient vapor-liquid contactarea is established and an efficient distillation is carried out whencompared to a vapor-liquid contactor using the self-promoting-fluiddispersion type structured packing having an inclined portion.Accordingly, a liquid load and vapor load can be established largely,without occurring a flooding.

For example, in a conventional vapor-liquid contactor using a packing(self-promoting-fluid dispersion type structured packing) having aspecific surface area of 500 m²/m³, a superficial F factor isestablished to be less than 1.6 m/s(kg/m³) (when the inner pressure ofthe column ranges from 0.08 to 0.4 MPa), or less than 1.0 m/s(kg/m³)(when the inner pressure of the column is more than 0.4 MPa). Incontrast, in said vapor-liquid contactor 2 a, 3 a, 4 a, each superficialF factor can be established to be more than 1.8 m/s(kg/m³) (when theinner pressure of the column ranges from 0.08 to 0.4 MPa), or more than1.0 m/s (kg/M³) (when the inner pressure of the column ranges from 0.4to 2.0 MPa).

In this regard, by using a vapor-liquid contactor 2 a, 3 a, 4 a, theheight of the column can be established lowly, and the costs requiredfor the production and construction of the apparatus can be reduced.Further, as the upper limit of the load is high, the production rate ofthe product can be significantly increased and reduced.

However, in the packing column, the inner pressure of the columngenerally tends to easily occur a flooding as the inner pressure of thecolumn is increased. It is difficult to apply the packing column to ahigh pressure column of the cryogenic air separation unit having amultiple distillation column. In contrast, in said vapor-liquidcontactor 2 a, a load can be established highly even at a high pressure;therefore, it is possible to apply to a high pressure column.

Accordingly, the cryogenic air separation unit wherein said vapor-liquidcontactor 2 a is applied to a high pressure column 2 has many advantagesin view of the power cost and product purity when compared to anapparatus wherein a sieve tray column is applied to a high pressurecolumn.

Further, to further improve a function of a minute distribution part B₁,B₂, a structure wherein at least one of said promoting-fluid-dispersiontype structured packing and a parallel plane sheet group is laminated inthe axial direction of the column, can be used as a minute distributionpart B₁, B₂.

FIGS. 25 and 26 shows one example of said parallel plane sheet group.The parallel plane sheet group 85 shown in FIG. 25 is formed of aplurality of plane sheets 85 a which are arranged in interval inparallel each other. This plane sheet 85 a is disposed along the axialdirection of the column. Each plane sheet 85 a is formed such that theedges perpendicular to the column axis is extended up to the adjacentinner wall of the column. Each plane sheet 85 a is fixed each other in astate narrowly inserted between the spacers (not shown) having athickness equivalent to these spaces.

The thickness of the plane sheet 85 a ranges preferably from 0.5 to 5mm, considering a structural strength. Also, the space of each planesheet 85 a ranges preferably from 3 to 10 mm, considering a liquiddispersion density. The plane sheet 85 a is preferably made of a metal,but it may be made of plastics. The pattern and material of spacer arenot particularly limited, but its size, for example, horizontal lengthor column axial length, is preferably small within the range retaining astructural strength such that a flow of plane sheet-like liquid membranemay not be prevented largely.

When said plane sheet group is provided, as a minute distribution partB₁, B₂, provided in the downward of a self-promoting-fluid-dispersiontype structured packing, a liquid minutely distributed in theself-promoting-fluid-distribution type structured packing is fed in aplane sheet group mounted downwardly to form a liquid membrane having anuniform thickness on the surface of each plane sheet and dropdownwardly; therefore, the flow rate of liquid becomes uniform over thedirection parallel to each plane sheet and the vertical direction to thecolumn axis. By doing so, a further minutely distributed liquid is fedin the non-promoting-fluid-dispersion type structured packing A₁, A₂.

Further, to increase more clearly a liquid dispersion density of thenon-promoting-fluid-dispersion type structured packing A₁, A₂, in alower edge portion of each plane sheet that constitutes a plane sheetgroup, a plurality of projecting part can be formed over the widthdirection of the plane sheet. Moreover, the width direction denotes adirection parallel to a plane sheet and vertical to a column axis.

FIG. 26 shows a plane sheet group 86 that forms this projecting part. Inthe lower edge portion 86 b of a plane sheet 86 a that constitutes aplane sheet group 86 shown herein, a plurality of V-shape projectingpart is formed over the whole width direction. A pitch of thisprojecting part 86 c ranges preferably from 3 to 10 mm.

As shown in FIG. 26, when a plurality of projecting parts 86 are, as aplane sheet that constitutes a plane sheet group, formed in the downedge portion 86 b, a liquid flowing down near the projecting part 86 cis collected near the edge of said projecting part 86 c and then droppeddown from the edge thereof.

In this regard, a liquid flowing down a surface of plane sheet 86 a istransferred to the lower edge portion and thereafter is prevented fromflowing along the lower edge portion 86 b and is prevented that the flowof liquid is inclined toward the width direction of plane sheet.Accordingly, the more minute liquid distribution can be achieved.

Usually, the non-promoting-fluid-dispersion type structured packing doesnot have a function to distribute the vapor stream positively. Hence, toincrease a distillation performance at the maximum, at least one vapordistributor that do a distribution of ascending vapor in the apparatus,is provided in the downward of the non-promoting-fluid-dispersion typestructured packing, considering a distillation of vapor stream.

As this vapor distributor, the self-promoting-fluid-dispersion typestructured packing, for example, as shown in FIGS. 6 and 7 is preferred.When the self-promoting-fluid-dispersion type structured packing is usedas a vapor distributor, a mist (fine droplet) is occurred at the bottomof said packing and the mist is collided on the thin sheet surface ofsaid packing and trapped in the liquid stream. Hence, the effect toprevent an entrainment is achieved.

Further, in the vapor-liquid contactor according to the presentinvention, since the non-promoting-fluid-dispersion type structuredpacking is used under a high load together with vapor and liquid, thespecific surface area of the self-promoting-fluid-dispersion typestructured packing used in a minute distribution part, etc. preferablyis equivalent to or smaller than that of thenon-promoting-fluid-dispersion type structured packing in order toprevent flooding.

Hereinafter, the effects of the present invention is clear referring tothe examples.

EXAMPLE 1

The computer simulation of a distillation operation using a cryogenicair separation unit shown in FIG. 1 was carried out. The vapor-liquidcontactor 2 a, 4 a in a high pressure column 2 and a crude argon column4 was assumed to have a liquid distributor E₁, a non-promoting-fluiddispersion type structured packing A₁, a liquid collector D, a liquiddistributor E₂ and a non-promoting-fluid dispersion type structuredpacking A₂ along the bottom from the peak of the column, as shown inFIG. 2.

Further, in each section 6˜9 of the vapor-liquid contactor 3 a, theliquid collector and vapor-liquid contactor F₂ was used, and in thesection 10, the liquid collector and vapor-liquid contactor F₁ was used.

As the non-promoting-fluid dispersion type structured packing A₁, A₂, astructured packing 91 was used. As the self-promoting-fluid dispersiontype structured packing B₁, B₂, a structured packing 71 was used. As therough distribution part C₁, C₂, a liquid distributor 41 was used.

The non-promoting-fluid distribution type structured packing A₁, A₂ usedin a vapor-liquid contactor 4 a in a crude argon column 4 was set tohave a specific surface area of 500 m²/m³. The inner pressure of thecolumn was set to about 0.1 MPa and the oxygen concentration in the feedargon was set to about 90%. As a result of simulation, a relationbetween the resultant packing height and the oxygen concentration in thevapor phase is shown with a solid line in FIG. 25. Further, in FIG thecolumn height 0 m denotes the bottom portion of the column.

Comparative Example 1

In the vapor-liquid contactor 4 a, a distillation operation was carriedout in the same manner as Example 1, using the same apparatus as shownin FIG. 1 except that the self-promoting-fluid dispersion typestructured packing of the same area was used instead of thenon-promoting-fluid dispersion type structured packing A₁, A₂. Theresults are shown with a dotted line in FIG. 27.

In a vapor-liquid contactor 4 a shown in FIG. 27, by using thenon-promoting-fluid dispersion type structured packing A₁, A₂, therequired packing height accounts for 60 percent when compared to thecase when the self-promoting-fluid dispersion type structured packing isused.

Next, to compare a pressure loss when the non-promoting-fluid-dispersiontype structured packing is used as a packing and when theself-promoting-fluid-dispersion type structured packing is used, thefollowing experiments were carried out.

EXAMPLE 2

The following experiments were carried out by using a distillationcolumn which is a vapor-liquid contactor shown in FIG. 28. Thisdistillation column (inner diameter 208 mm, prepared from transparentvinyl chloride) includes a rough dispersion part C₃, a minutedistribution part B₃, and a non-promoting-fluid-distribution typestructured packing A₃ over the bottom portion from the top portion ofthe column.

As the rough distribution part C₃, the same part as shown in FIG. 4 wasused. As the minute distribution part B₃, the self-promoting-fluiddispersion type structured packing 2 elements denoted by the referencenumber 87 having a specific surface area of 500 m²/m³ and a height of100 mm, the parallel plane plate group 85 (height 50 mm) as shown inFIG. 26, and a parallel plane sheet group 86 (height 50 mm) as shown inFIG. 27 were used in the order from the top portion.

In this case, two parallel plane sheet groups 85 a, 86 a of two parallelplane sheet groups 85, 86 were disposed such that a parallel plane sheetthat constitutes each group may have an intersecting relation in thevertical direction.

As the non-promoting-fluid-dispersion type structured packing A₃. thepacking having a specific surface area of 375 m/m and a height of 600 mmas shown in FIG. 15 was used. The total height of the minutedistribution part B₃ and the non-promoting-fluid dispersion typestructured packing A₃ is 900 mm.

The total pressure loss of a rough distribution part C₃, a minutedistribution part B₃ and a non-promoting-fluid dispersion typestructured packing A₃ was determined by using as a fluid a freon havingthe same viscosity as air and changing a superficial F factor under thewhole reflux condition and pressure 130 kPa.

Comparative Example 2

For comparison, an experiment was carried out by using a distillationcolumn mounted with a self-promoting-fluid dispersion type structuredpacking 5 elements of 500 m²/m³, height 207 mm (whole packed height 1035mm), in the downward of the distillation column using as a packing aself-promoting-fluid dispersion type structured packing, i.e., roughdistribution part C₃.

As the self-promoting-fluid dispersion type structured packing, the samepacking as used in a minute distribution part B₃ shown in FIG. 28 wasused. In the same manner as in Example 2, a pressure loss under eachcondition was determined by using as a fluid a freon having the sameviscosity as air and changing a superficial F factor under the wholereflux condition.

FIG. 29 is a graph showing a pressure loss over the unit height relativeto a superficial F factor. As shown in FIG. 29, when thenon-promoting-fluid dispersion type structured packing was used as apacking (Example 2) exhibited a clearly lower pressure loss than whenthe self-promoting-fluid dispersion type structured packing was used(Comparative Example 2).

From the above experimental result, it can be seen that the distillationcolumn used in Example 2 can be designed in smaller column diameter andreduce the cost required for the production and construction ofapparatus, when compared to the distillation column used in comparativeexample 2.

Next, a comparison of liquid distribution when a minute distributionpart is mounted in the distillation column and when a minutedistribution part is not mounted in the distillation column was carriedout.

EXAMPLE 3

As an example that a minute distribution part is mounted in thedistillation column, the degree of dispersion of liquid under eachcondition was observed by using a distillation column of Example 2 shownin FIG. 28 and using as a fluid a freon having the same viscosity asair. Further, a liquid flow in the column and a pattern in liquiddistribution was taken by a video.

Comparative Example 3

As an example that a minute distribution part is not mounted in thedistillation column, experiment was carried out in the same manner asExample 3 and by using the same distillation column as in Example 3except that a minute distribution part is not mounted.

FIGS. 30 and 31 are a photograph taken from a fluid pattern droppingdown from the lower edge of the non-promoting-fluid dispersion typestructured packing of the distillation column of Example 3 andComparative Example 3 under the condition of a pressure 130 kPa, liquidload converted into gas load 2 m/s (kg/m³)^(½).

It can be confirmed from FIG. 30 that when a packing has a minute liquiddistribution part (Example 3), a droplet flows and drops down in thelinear direction from each stream channel, and that each of thesedroplets is distributed uniformly over the whole column.

In contrast, it can be seen that when a minute distribution part is notmounted (Comparative Example 3), the droplet is not evenly distributedas shown in FIG. 31.

What is claimed is:
 1. A gas separation method which separates a vapormixture comprising at least two components into the two components usinga vapor-liquid contactor in a column; wherein said method comprises: a)providing a vapor-liquid contactor including a non-promoting-fluiddispersion structured packing formed of various thin-sheets or tubeswhich direct the flow of said mixture vertically, saidnon-promoting-liquid-dispersion structured packing having a specificsurface area of 350 m²/m³ or more; and b) contacting said vapor andliquid countercurrently on the surface of said packing under a pressureof from 0.08 to 0.4 MPa, and at a vapor load of 1.8 m/s (kg/m³)^(½) ormore in superficial F factor.
 2. A gas separation method which separatesa vapor mixture comprising at least two components into the twocomponents using a vapor-liquid contactor in a column; wherein saidmethod comprises: a) providing a vapor-liquid contactor including anon-promoting-fluid dispersion structured packing formed of variousthin-sheets or tubes which direct the Pow of said mixture vertically,said non-promoting-liquid-dispersion structured packing having. specificsurface area of 350 m²m³ or more, and b) contacting said vapor andliquid countercurrently on the surface of said packing under a pressureof from 0.4 to 2.0 MPa, and at a vapor load of 1.0 m/s (kg/m³)^(½) ormore in superficial F factor.